Data types

This newtype is Haskell's () with unit of dimension u as
a phantom type.

This type has no direct use in Wumpus-Core, but it is useful
for higher-level software a - it has instances of the affine
classes which cannot be written for () (Wumpus-Basic
uses it for the Graphic type.)

Make a circle from Bezier curves - the number of subdivsions
controls the accuracy or the curve, more subdivisions produce
better curves, but less subdivisions are better for rendering
(producing more efficient PostScript).